Foot controlled switch



Now/3, 1931. B. s. T. BISHOP 1,830,255

FOOT CONTROLLED SWITCH Filed Oct. 29, 1929 2 Sheets-Sheet l Nov. 3, 1931. B. s. T. BISHOP v FOOT CONTROLLED SWITCH Filed on. 29, 1929 2 Sheets- Sheet 2 jaw-r Patented Nov. 3, 1931 UNITED STATES PATENT OFFICE BENJAMIN S. T. BISHOP, OF SHREWSBURY, MASSACHUSETTS, ASSIGNOR TO LELAND- GIFFOBD COMPANY, A CORPORATION OF MASSACHUSETTS FOOT CONTROLLED SWITCH Application filed October 29, 1929. Serial No. 403,315.

- This invention relates to the operation and control of a switch for the motor for operating a machine tool or'the like.

The principal objects of the invention are to provide an operating means for the switch adapted to be controlled by the foot of the operator to turn it to either extreme position; to provide suitable yielding means for turning it to neutral position when the foot is taken off either pedal; to provide convenient and simple yielding means whereby the sudden depression of the pedal in either direction will be prevented from doing any injury to the operating mechanism; and to provide a simple connection between the operating mechanism and the electric switch for actuating the latter.

Other objects and advantages of the invention will appear hereinafter. Reference is to be had to the accompanying drawings in which 1 Fig. 1 is a side view of a. part of the upright or support of a machine tool, such as a drill tapping machine or the like, preferably of the vertical type, showing this invention as applied thereto when a three phase motor is used;

Fig. 2 isa side view of the switch operating mechanism, looking in the direction of the arrow 2 in Fig. 1

Fig. 3'is a sectional View of the electrical switch itself on the line 3-3 of Fig. 1;

Fig. 4 is an end view of the switch operat ing mechanism on enlarged scale shown in neutral position;

' Fig. 5 is a plan of the same;

Fig. 6 is an end view like Fig. 4 of the oscillatable element of the switch operating mechanism removed from the other parts;

Fig. 7 is a plan of'the shaft which transmits the motion from: the foot pedal to the make-and-break part of the switch;

Fig. 8 is an end view of the same, and

Fig. 9 is an end view of the make-andbreak part of the switch.

This invention can be applied to machine tools and other apparatus of various kinds and is intended for the purpose of turning on a motor and stopping it. The wiring; is shown for a three phase motor. The treadle 10, which is mounted at the base of the machine, extends in both directions from its shaft 11 on which it is fixed with means at each end for turning it down at that end.

On the shaft 11 is an arm 12 connected by a link 13 with a lever 14. This lever is provided on one side with a split arm and on the other side with a projection 15. In. this split arm is a stud 16 with which the link 13 is directly connected. or, forming a part thereof. This lever is freely mounted on a shaft 17 which is provided with a diametrical perforation in which enters the end of a steel spring 18, the other end of which is secured between the bifurcations of the main arm of the lever 14. Therefore the oscillation of this lever 14 will be transmitted to the shaft 17 through this spring yieldingly, thus avoiding breakage if the treadle is pushed down suddenly. The lever 14 is supported on the shaft 17 through a hollow hub 19 on a casing 20, these three parts not being keyed together or otherwise connected to rotate together except by the spring 18. p

The casing 20 is fixed to the frame or other i. stationary part of the machine on which it is located. On this casing are three stops 21, 22 and 23 cast on it as lugs. Coiled around the hub 19 is a spring 24 having two ends proiecting therefrom. one on either side of the lug 23 and also passing on opposite sides of the short arm 15 which extends from the lever 14 far enough to receive this spring on both sides. It will be seen that the coil spring engaging the lug 23 on both sides and the arm 15. any pressure on the treadle 10 at either end to force the lever 14 out of neutral position in either direction will put a tension on this spring. When the pressure on the treadle is 90 relieved. this spring 24 will swing the lever 1 14 back to neutral position, as shown in Fi 4. I

The switch is shown as provided with three line wires 38. in case the invention is to be used. with a. three phase motor. and three motor wires 40 as usual. The energizing of a magnet 37 will swing four plates 39 to complete four circuits through the three pairs of contacts 3333. Three of the circuits connect the motor with the three mains 38 through wires 40.

The shaft 17 passes of course all the way through the hub 19 and at its other end is provided with a fibre cam 25 separated from the shaft by a fibre washer. This cam lies between two electrical contacting plates 26 which are independently pivoted and are both pressed against the cam by a double spring 27. When the lever is in neutral position, the cam will be in the position shown in Fig. 9, and one plate 26 will be in contam with an insulating stop 28 while the other engages a contact 30 located at the opposite face of the stop.

When, however, the treadle is forced'down in one direction to start the motor, the cam will be turned up to force the upper plate 26 against a contact 29. When the treadle is depressed in the other direction the lower plate 26 will be moved away from the contact 30 on the other side. These two contacts are connected by wires 32 and 31 respectively with a contact 33 and a line 40. The two plates 26 are electrically connected with a binding screw 35, which, by a wire 36, is connected with an electro-magnet 37, which in turn is connected with a line 38. Now when the parts are in the position shown in Fig. 1, connection is made from the line 38, magnet 37 and wire 36 to the wire 31 and contact 33. Thus the circuit is incomplete.

If the right end of the treadle is depressed to start the motor the parts assume the position shown in Fig. 1. The upper plate 26 engages the contact 29 and the arm 15 the stop 21. The circuit is then completed through plate 26, contact 29, wire 32 and motor line 40. This energizes the magnet 37 which raises the plunger 41 and swings a lever 42 on its pivot 43. This closes all the contacts 33 by the several plates 39. The motor is connected up andstarts. Now, if the operator steps off the treadle, the spring 24 brings the lever 14 to neutral. This breaks the circuit at 29 obviously, but it is maintained through 30, 31, 33, 39, 33 (at the right in Fig. 1) 38, 33, 39, 33 and 40. So the motor continues to run. 1

To stop the motor it is necessary to depress the treadle at the opposite end which breaks the circuit through the electro-magnet at the contacts 26-30. When the lever 14 is again restored to neutral, the parts will be in the position first described, namely, with the magnet circuit broken at the right hand contacts 33 and the motor circuit-s open.

It will be seen therefore that the treadle can be pushed down from one endto start the operating motor and from the other end to stop it and that in either case as soon as the foot is taken off the treadle, the lever 14 will automatically return to a neutral position without stopping or starting the motor and ready for the starting or stopping action to be performed. It will also be seen that no sudden depression of the treadle in either direction will be transmitted rigidly to the other parts. This eliminates the danger of breaking parts by that means.

Although I have illustrated and described only one form of the invention I am aware of the fact that modifications can be made .therein by any person skilled in the art without departing from the scope of the invention as expresed in the claims. Therefore I do not wish to be limited in this respect but what I do claim is 1. In a switch operating device, the combination with a switch for turning on and off the power comprising two pivoted contact plates, of an insulating cam located be tween said plates, a shaft on which the cam is mounted,an arm pivoted on the same axis as the shaft, a spring connection between the arm and the shaft, a lever having arms projecting in opposite directions from its center and connected with the first named arm, whereby the lever can be depressed at either end to move the first named arm in either di- 3 rection and the action will be transmitted to said shaft and a switch yieldingly.

, 2. In an operating device for an electric switch, the combination of a shaft having means for operating the switch, a spring fixed to said shaft at one end, a lever pivoted on the same axis as the shaft, oscillatable relatively to the shaft, and connected with said spring at a distance from the shaft and constituting the only means for transmitting motion to the shaft, and means for operating the lever.

- 3. In an operating device for an electric switch, the combination of a shaft having means for operating the switch, a spring fixed to said shaft at one end, a lever pivoted on the same axis as the shaft and connected with said spring at a distance from the shaft and constituting the only means for transmitting motion to the shaft, means for operating the lever, the lever having an arm projecting on the opposite side of said shaft, a spring coiled on the axis of said shaft and having its'ends engaging the opposite sides of thesaid arm of the lever, whereby the spring is movable with the lever, and a. fixed lug between the two ends of the spring for preventing the motion of one end whenever the lever is moved out of neutral position and putting pressure on the arm of the lever to return it to neutral position.

4. In a switch operating device, the combination with a switch, a shaft for operating said switch, a coiled spring concentric with the shaft and having its two ends projecting outwardly, a lever pivoted on said shaft and yieldingly connected therewith, and means whereby the shaft will be turned back yieldingly to neutral position if the pressure for turning it is removed.

5. In a switch operating device, the combination with a switch comprising two independently pivoted contact plates, an insulating cam located between them and adapted to be turned out of neutral position to move either plate out of neutral position, a shaft for operating said cam, a coiled spring concentric with the shaft and having its two ends projecting outwardly in a substantially radial direction, a lever pivoted on said shaft and connected therewith, a fixed lug, the opposite sides of which are engaged by the pro- ]ecting ends of said spring, said lever having an arm adjacent to said lug, the opposite sides of which are engaged by said spring ends, means connected with said lever to operate it, whereby the turning of the lever out of neutral position will take place in opposition to said spring through one of its ends and the spring will turn the lever and shaft back to neutral position when pressure is removed from said means.

6. In a switch operating device, the combination with an electric switch comprising a pair of normally parallel plates independently pivoted on an axis at one end, an insulating stop for holding said plates apart, a contact at one end of the stop with which one of said plates engages when the switch is in neutral position, a contact spaced from the other side of said stop adapted to be engaged by the other plate when the switch is turned for the purpose of turning on the current, a connection from the last named contact to one side of an electric line, a connection from both of said plates to the other end of the line, a connection from the contact on the stop, normally broken, to the first named end of the line and means for completing the normally broken circuit when the switch is turned to turn on power and for connecting the motor with power lines, whereby the circuit will be first closed through the contact spaced from the stop and then closed per" manently after this contact is broken.

In testimony whereof I have hereunto aflixed my signature.

BENJAMIN S. T. BISHOP. 

